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Published October 2019 | Published + Submitted
Journal Article Open

Precision Projector Laboratory: Detector Characterization with an Astronomical Emulation Testbed


As astronomical observations from space benefit from improved sensitivity, the effectiveness of scientific programs is becoming limited by systematics that often originate in poorly understood image sensor behavior. Traditional, bottom-up detector characterization methods provide one way to model underlying detector physics and generate ever more faithful numerical simulations, but this approach is vulnerable to preconceptions and over-simplification. The alternative top-down approach is laboratory emulation, which enables observation, calibration, and analysis scenarios to be tested without relying on a complete understanding of the underlying physics. This complements detector characterization and simulation efforts by testing their validity. We describe a laboratory facility and experimental testbed that supports the emulation of a wide range of mission concepts such as gravitational weak lensing measurements by the Wide Field Infrared Survey Telescope and high precision spectrophotometry of transiting exoplanets by James Webb Space Telescope. An Offner relay projects readily customizable "scenes" (e.g., stars, galaxies, and spectra) with very low optical aberration over the full area of a typical optical or near-infrared image sensor. f  /  8 and slower focal ratios may be selected, spanning those of most proposed space missions and approximating the point spread function (PSF) size of seeing limited ground-based surveys. Diffraction limited PSFs are projected over a wide field of view and wavelength range to deliver highly predictable image patterns down to subpixel scales with stable intensity and fine motion control. The testbed enables realistic validation of detector performance on science-like images, which aids mission design and survey strategy as well as targeted investigations of various detector effects.

Additional Information

© 2019 Society of Photo-optical Instrumentation Engineers (SPIE). Paper 19042SS received Apr. 24, 2019; accepted for publication Jul. 30, 2019; published online Aug. 23, 2019. We sincerely thank the members of Caltech Optical Observatories who contributed to the construction and maintenance of the PPL testbed: Dave Hale, Jennifer Milburn, Hector Rodriguez, Patrick Murphy, Michael Feeney, Justin Belicki, Alex Delacroix, and former team members Eric Jullo and Viswa Velur, who were key players in the early stages of development. Thanks to Warren Holmes and the Euclid detector working group for lending the H2RG detector used in subpixel and brighter-fatter effect measurements. This work was carried out at the Jet Propulsion Laboratory, California Institute of Technology, under a contract with the National Aeronautics and Space Administration. AAP acknowledges support from the Italian Ministry of Foreign Affairs and International Cooperation, Directorate General for Country Promotion.

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Published - 041503_1.pdf

Submitted - 1801.06599.pdf


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August 19, 2023
October 19, 2023